Question 1

Which of the following best describes the semi-conservative model of DNA replication as demonstrated by the Meselson-Stahl experiment?

Accepted Answer

Each new DNA molecule consists of one old (parental) strand and one newly synthesized strand.

Question 2

During DNA replication in E. coli, which enzyme is responsible for relieving the tension ahead of the replication fork caused by unwinding of the DNA?

Accepted Answer

DNA gyrase (a type of topoisomerase)

Question 3

What is the primary function of DNA polymerase I during DNA replication in E. coli?

Accepted Answer

Removal of RNA primers and replacement with DNA nucleotides

Question 4

Which of the following statements about Okazaki fragments is correct?

Accepted Answer

They are short DNA fragments synthesized on the lagging strand during DNA replication.

Question 5

In the Meselson-Stahl experiment, what would have been observed in Generation 1 if DNA replication was conservative?

Accepted Answer

Two distinct bands: one for 15N-DNA and one for 14N-DNA

Question 6

Which property distinguishes DNA polymerase I from DNA polymerase III in E. coli?

Accepted Answer

DNA polymerase I has 5' to 3' exonuclease activity, while DNA polymerase III does not.

Question 7

Which enzyme is responsible for synthesizing the RNA primer required for DNA replication in E. coli?

Accepted Answer

Primase

Question 8

What is the role of single-stranded binding proteins (SSBPs) during DNA replication?

Accepted Answer

They stabilize single-stranded DNA and prevent reannealing of the strands.

Question 9

Which of the following best describes the directionality of DNA synthesis by DNA polymerases?

Accepted Answer

DNA polymerases synthesize DNA in the 5' to 3' direction.

Question 10

A student is analyzing a DNA replication fork. Which strand is synthesized continuously, and in which direction relative to the replication fork movement?

Accepted Answer

The leading strand is synthesized continuously in the same direction as the replication fork movement.

Question 11

Which of the following equations correctly represents the relationship between density ($$\rho$$), mass ($$m$$), and volume ($$V) as $$used in CsCl density gradient centrifugation?

Accepted Answer

$$\rho = \frac{m}{V}$$

Question 12

During DNA replication, which enzyme is responsible for sealing the 'nicks' left after RNA primer removal and replacement with DNA?

Accepted Answer

DNA ligase

Question 13

A mutation in the ε subunit of DNA polymerase III is most likely to affect which property of the enzyme?

Accepted Answer

Proofreading (3' to 5' exonuclease activity)

Question 14

Which of the following statements about the Meselson-Stahl experiment is correct?

Accepted Answer

It used isotopes of nitrogen to distinguish between old and new DNA strands.

Question 15

If the sequence of a DNA template is 3'-GGCTACCTGGATTCA-5', and an RNA primer of 8 nucleotides is synthesized starting at the underlined base, what is the sequence of the RNA primer?

Accepted Answer

5'-CCGAUGGA-3'

Question 16

Which of the following best explains why DNA polymerases require a primer to begin synthesis?

Accepted Answer

DNA polymerases can only add nucleotides to a free 3'-OH group.

Question 17

Which of the following is a correct description of a replicon in E. coli?

Accepted Answer

A DNA molecule that replicates from a single origin of replication

Question 18

Which of the following steps occurs first during DNA replication in E. coli?

Accepted Answer

Localized unwinding of DNA at the origin of replication

Question 19

Which of the following statements about the directionality of DNA synthesis and proofreading is correct?

Accepted Answer

DNA synthesis occurs in the 5' to 3' direction, while proofreading (exonuclease activity) occurs in the 3' to 5' direction.

DNA Replication: Mechanisms, Enzymes, and Experimental Evidence

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